U.S. patent application number 16/205340 was filed with the patent office on 2020-06-04 for papermaking fabrics having machine and cross-machine direction elements and paper products made therewith.
The applicant listed for this patent is Kimberly-Clark Worldwide, Inc.. Invention is credited to Mark Alan Burazin, Christopher Steven LeCount, Kevin Joseph Vogt, Richard Allen Zanon.
Application Number | 20200173113 16/205340 |
Document ID | / |
Family ID | 70849632 |
Filed Date | 2020-06-04 |
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United States Patent
Application |
20200173113 |
Kind Code |
A1 |
Vogt; Kevin Joseph ; et
al. |
June 4, 2020 |
PAPERMAKING FABRICS HAVING MACHINE AND CROSS-MACHINE DIRECTION
ELEMENTS AND PAPER PRODUCTS MADE THEREWITH
Abstract
The present invention discloses tissue products, specifically
rolled paper towel products, such as one, two or three ply tissue
products having a basis weight greater than about 35 gsm and a GMT
greater than about 1,500 g/3''. The products have a
three-dimensional surface, typically the air contacting surface,
comprising substantially continuous machine direction (MD) oriented
elements, discrete cross-machine direction (CD) oriented elements
and discrete MD oriented valleys having valley sidewalls formed by
the MD oriented elements and valley endwalls formed by the CD
oriented elements. The discrete valleys generally have a length
greater than about 10.0 mm. The CD oriented elements comprise a
relatively small percentage of the tissue surface area, such as
less than about 15 percent, yet the tissue products display good
anti-nesting properties when spirally wound into rolls, such as a
Roll Structure greater than about 1.75.
Inventors: |
Vogt; Kevin Joseph; (Neenah,
WI) ; LeCount; Christopher Steven; (Greenville,
WI) ; Zanon; Richard Allen; (Appleton, WI) ;
Burazin; Mark Alan; (Oshkosh, WI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kimberly-Clark Worldwide, Inc. |
Neenah |
WI |
US |
|
|
Family ID: |
70849632 |
Appl. No.: |
16/205340 |
Filed: |
November 30, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A47K 10/16 20130101;
D21H 27/40 20130101; D21H 27/02 20130101; D21H 27/005 20130101 |
International
Class: |
D21H 27/00 20060101
D21H027/00; D21H 27/02 20060101 D21H027/02; D21H 27/40 20060101
D21H027/40; A47K 10/16 20060101 A47K010/16 |
Claims
1. A rolled paper towel product comprising a spirally wound single
tissue sheet having a fabric side and an opposite air contacting
side and a machine direction and a cross-machine direction, the ply
having a basis weight from 30 to 60 gsm and a geometric mean
tensile (GMT) strength greater than about 1,500 g/3'', wherein the
air contacting side of the ply comprises a plurality of discrete
valleys having a length greater than about 10 mm.
2. The rolled paper towel product of claim 1 further comprising a
plurality of machine direction (MD) oriented elements spaced apart
from one another in the cross-machine direction (CD) of the ply,
the spaced apart MD oriented elements forming a the sidewalls of
the plurality of discrete valleys.
3. The rolled paper towel product of claim 1 further comprising a
plurality of cross-machine direction (CD) oriented elements spaced
apart from one another in the machine direction of the ply, the
spaced apart CD oriented elements forming the endwalls of the
plurality of discrete valleys.
4. The rolled paper towel product of claim 2 wherein the plurality
of MD oriented elements are substantially parallel to one another
and have an element angle from about 0.5 to about 10 degrees.
5. The rolled paper towel product of claim 3 wherein the plurality
of CD oriented elements are substantially parallel to one another
and have an element angle from about 20 to about 40 degrees.
6. The rolled paper towel product of claim 3 wherein the plurality
of CD oriented elements have a length from about 3.0 to about 10.0
mm.
7. The rolled paper towel product of claim 3 wherein the plurality
of CD oriented elements have a height from about 700 to about 900
.mu.m.
8. The rolled paper towel product of claim 1 wherein the discrete
valleys have a length from about 10 to about 30 mm and a width from
about 1.0 to about 3.0 mm.
9. The rolled paper towel product of claim 1 having a caliper
greater than about 700 .mu.m and a roll structure greater than
about 1.75.
10. The rolled paper towel product of claim 1 having a roll bulk
greater than about 16 cc/g and a roll structure greater than about
1.75.
11. The rolled paper towel product of claim 1 having a firmness
from about 6.0 to about 8.0 and a roll structure greater than about
1.75.
12. The rolled paper towel product of claim 1 having a geometric
mean tensile (GMT) from about 2,000 to about 4,000 g/3'' and a
Stiffness Index less than about 5.0.
13. The rolled paper towel product of claim 1 wherein the tissue
sheet comprises two or more plies and is embossed.
14. The rolled paper towel product of claim 1 wherein the tissue
sheet comprises a single ply and is unembossed.
15. A tissue sheet having an air side and opposite fabric side,
wherein the air side comprises discrete CD oriented elements having
an element angle greater than 20 degrees and extending between
spaced apart substantially continuous MD oriented elements, the
tissue sheet having a basis weight from about 30 to about 60 gsm
and a geometric mean tensile (GMT) greater than about 1,500
g/3''.
16. The tissue sheet of claim 15 further comprising a plurality of
discrete valleys having valley sidewalls defined by the spaced
apart substantially continuous MD oriented elements and valley
endwalls defined by the discrete CD oriented elements.
17. The tissue sheet of claim 16 wherein the discrete valleys have
a length from about 10 to about 30 mm.
18. The tissue sheet of claim 15 wherein the substantially
continuous MD oriented elements are substantially parallel to one
another and have an element angle from about 0.5 to about 10
degrees and the discrete CD oriented elements have an element angle
from about 20 to about 40 degrees.
19. The tissue sheet of claim 15 wherein the discrete CD oriented
elements have a height from about 600 to about 900 .mu.m.
20. A tissue product having a three-dimensional surface topography
comprising substantially continuous MD oriented elements, discrete
CD oriented elements, and discrete MD oriented valleys having
spaced apart sidewalls and endwalls, wherein the sidewalls of the
MD oriented valleys are formed by the MD oriented elements and the
endwalls are formed by the CD oriented elements and wherein the
discrete valleys have a length greater than about 10 mm, wherein
the tissue product has a basis weight greater than about 35 gsm and
a GMT greater than about 1,500 g/3''.
Description
BACKGROUND
[0001] For rolled tissue products, such as bathroom tissue and
paper towels, consumers generally prefer firm rolls having a large
diameter. A firm roll conveys superior product quality and a large
diameter conveys sufficient material to provide value for the
consumer. From the standpoint of the tissue manufacturer, however,
providing a firm roll having a large diameter is a challenge. In
order to provide a large diameter roll, while maintaining an
acceptable cost of manufacture, the tissue manufacturer must
produce a finished tissue roll having higher roll bulk. One means
of increasing roll bulk is to wind the tissue roll loosely. Loosely
wound rolls however, have low firmness and are easily deformed,
which makes them unappealing to consumers. As such, there is a need
for tissue rolls having high bulk as well as good firmness.
[0002] Furthermore, it is desirable to provide a rolled tissue
product having a high basis weight tissue sheet that is also soft.
To provide a tissue product that is perceived as being soft, the
tissue manufacturer is faced with a myriad of choices, including
altering the surface topography of the tissue product so that the
user perceives it as being smooth. Smooth, high basis weight
products however, are difficult to wind into firm, high bulk
finished products.
[0003] The challenge of balancing bulk, firmness, and sheet
smoothness is particularly acute when winding through-air dried
tissue products since much of the product bulk is achieved by
molding the embryonic tissue web into the papermaking fabric which
is increasingly difficult at higher basis weights and the molded
structure may need to be calendered to increase sheet smoothness.
Hence the tissue manufacturer must strive to economically produce a
tissue roll that meets these often-contradictory parameters of high
bulk, firm and smooth tissue products at an acceptable cost.
SUMMARY
[0004] It has now been discovered that certain consumer preferred
properties of tissue products, including through-air dried tissue
products, can be improved by modifying the fabrics used in the
process of manufacturing the tissue product. The resulting tissue
products, particularly rolled tissue products, have both a high
degree of bulk and firmness, particularly for rolls made from
relatively soft sheets.
[0005] Accordingly, in one embodiment the present invention
provides a tissue sheet having an air side and opposite fabric
side, wherein the air side comprises discrete CD oriented elements
having an element angle greater than 20 degrees and extending
between spaced apart substantially continuous MD oriented elements,
the tissue sheet having a basis weight from about 30 to about 60
gsm and a geometric mean tensile (GMT) greater than about 1,500
g/3''.
[0006] In another embodiment the present invention provides a
rolled paper towel product comprising a spirally wound single
tissue sheet having a fabric side and an opposite air contacting
side and a machine direction and a cross-machine direction, the ply
having a basis weight from 30 to 60 gsm and a geometric mean
tensile (GMT) strength greater than about 1,500 g/3'', wherein the
air contacting side of the ply comprises a plurality of discrete
valleys having a length greater than about 10 mm.
[0007] In yet another embodiment the present invention provides a
tissue product having a three-dimensional surface topography
comprising a plurality of MD oriented elements, such as ridges,
separated from one another by a plurality of MD oriented valleys,
wherein at least a portion of the MD oriented valleys are
discontinuous. The discontinuous MD oriented valleys may have a
length of about 10 mm or greater, such as about 15 mm or greater,
such as about 20 mm or greater, such as from about 10 to about 30
mm, such as from about 15 to about 30 mm, such as from about 20 to
about 30 mm.
[0008] In still other embodiments the present invention provides a
tissue product having a fabric side and an opposed air side,
wherein the air side comprises MD and CD oriented elements having
upper surface planes lying above the lowest surface plane of the
air side. In particularly preferred embodiments the MD oriented
elements are substantially continuous and the CD oriented elements
are discrete and both elements have a height, generally measured as
the z-directional distance between the uppermost surface plane of
the element and the lowermost surface plane of the product, of at
least about 300 .mu.m.
[0009] In another embodiment the present invention provides a
method of making a through-air dried tissue sheet comprising (a)
depositing an aqueous suspension of papermaking fibers onto a
forming fabric to form a wet web; (b) dewatering the wet web to
yield a partially dewatered web having a consistency from about 20
to about 30 percent; (c) transferring the partially dewatered web
to a through-air drying fabric having a plurality of interwoven
shute and warp filaments, the fabric having a web contacting
surface and an opposite machine contacting surface, the web
contacting surface comprising a plurality of spaced apart machine
direction (MD) oriented protuberances defining a plurality of
valleys having a valley bottom surface plane there between, and a
plurality of cross-machine direction (CD) oriented protuberances,
wherein the MD and CD oriented protuberances have an upper surface
that lies above the valley bottom surface plane, wherein the web is
macroscopically rearranged to conform to the surface of the
through-air drying fabric; and (e) through-air drying the web to
yield a through-air dried tissue web.
[0010] In still other embodiments the present invention provides a
rolled paper towel comprising a single-ply paper towel spirally
wound about a core, the rolled product having a geometric mean
tensile (GMT) strength greater than about 1,500 g/3'', a sheet bulk
greater than about 16 cc/g, a roll bulk greater than about 15 cc/g
and a roll firmness greater than about 6.0 mm.
[0011] In yet other embodiments the present invention provides a
rolled paper towel comprising a multi-ply paper towel spirally
wound about a core, the rolled paper towel product having a
geometric mean tensile (GMT) strength greater than about 2,000
g/3'', a sheet bulk greater than about 16 cc/g, a roll bulk greater
than about 15 cc/g and a roll firmness greater than about 6.0
mm.
DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is top plan view of a papermaking fabric according to
one embodiment of the present invention;
[0013] FIG. 2 is top plan view of a papermaking fabric according to
one embodiment of the present invention;
[0014] FIG. 3 is an image of a papermaking fabric according to
another embodiment of the present invention taken at 100.times.
magnification using a Keyence VHX-5000 Digital Microscope (Keyence
Corporation, Osaka, Japan);
[0015] FIG. 4 is a profilometry scan of a papermaking fabric
according to another embodiment of the present invention taken
using a FRT MicroSpy.RTM. Profile profilometer (FRT of America,
LLC, San Jose, Calif.);
[0016] FIGS. 5A-5C illustrate various patterns of nonwoven elements
useful in the present invention;
[0017] FIG. 6 is a 3D image of the air side of a tissue sheet
according to one embodiment of the present invention obtained using
a Keyence microscope and imaging software as described herein;
[0018] FIG. 7 is a 3D height map of the air side of the tissue
sheet of FIG. 6;
[0019] FIGS. 8A-8C illustrate the cross-machine direction profile
of the air side of the tissue sheet of FIG. 6 obtained using a
Keyence Microscope and imaging software as described herein;
and
[0020] FIGS. 9A-9C illustrate the machine direction profile of the
air side of the tissue sheet of FIG. 6 obtained using a Keyence
Microscope and imaging software as described herein.
DEFINITIONS
[0021] As used herein, a "tissue product" generally refers to
various fibrous structures, particularly sheets of fibrous material
that may be spirally wound about a core, such as facial tissue,
bath tissue, paper towels, napkins, and the like.
[0022] As used herein, the term "basis weight" generally refers to
the bone dry weight per unit area of a tissue and is generally
expressed as grams per square meter (gsm). Basis weight is measured
using TAPPI test method T-220. Normally, the basis weight of a
tissue product of the present invention is greater than about 10
grams per square meter (gsm), such as from about 10 to about 80
gsm.
[0023] As used herein, the term "ply" refers to a discrete element
of a tissue product. Individual plies may be arranged in
juxtaposition to each other. The term may refer to a plurality of
web-like components such as in a multi-ply facial tissue, multi-ply
bath tissue, multi-ply paper towel, multi-ply wipe, or multi-ply
napkin, which may comprise two, three, four or more individual
plies arranged in juxtaposition to each other where one or more
plies may be attached to one another such as by mechanical or
chemical means.
[0024] As used herein, the term "layer" refers to a plurality of
strata of fibers, chemical treatments, or the like, within a
ply.
[0025] As used herein, the terms "layered tissue web"
"multi-layered tissue web," "multi-layered web," and "multi-layered
paper sheet," generally refer to sheets of paper prepared from two
or more layers of aqueous papermaking furnish which are preferably
comprised of different fiber types. The layers are preferably
formed from the deposition of separate streams of dilute fiber
slurries upon one or more endless foraminous screens. If the
individual layers are initially formed on separate foraminous
screens, the layers are subsequently combined (while wet) to form a
layered composite web.
[0026] As used herein, the term "papermaking fabric" means any
fabric useful in the manufacture of a fibrous structure, such as a
tissue sheet, either by a wet-laid process or an air-laid process.
Specific papermaking fabrics within the scope of this invention
include forming fabrics; transfer fabrics conveying a wet web from
one papermaking step to another, such as described in U.S. Pat. No.
5,672,248; as molding, shaping, or impression fabrics where the web
is conformed to the structure through pressure assistance and
conveyed to another process step, as described in U.S. Pat. No.
6,287,426; as creping fabrics as described in U.S. Pat. No.
8,394,236; as embossing fabrics as described in U.S. Pat. No.
4,849,054; as a structured fabric adjacent a wet web in a nip as
described in U.S. Pat. No. 7,476,293; or as a through-air drying
fabric as described in U.S. Pat. Nos. 5,429,686, 6,808,599 and
6,039,838. The fabrics of the invention are also suitable for use
as molding or air-laid forming fabrics used in the manufacture of
non-woven, non-cellulosic webs such as baby wipes.
[0027] As used herein, the "fabric side" of the tissue sheet is the
side of the sheet brought into facing contact with the papermaking
fabric of the present invention during manufacture and the "air
side" of the sheet is the side facing away from the papermaking
fabric. For example, in through-air drying processes the "fabric
side" of the tissue sheet contacts the through-air drying fabric as
it is conveyed over the through-air dryer and the "air side" of the
sheet faces away from the through-air drying fabric. When the sheet
is wound into a roll of product by winding the sheet concentrically
about a core it is often preferred that the sheet is wound such
that the air side of the sheet faces inwardly towards the core and
the fabric side of the sheet faces outwardly towards the
consumer.
[0028] As used herein the term "machine direction" (MD) generally
refers to the direction in which a tissue web or product is
produced. The term "cross-machine direction" (CD) refers to the
direction perpendicular to the machine direction.
[0029] As used herein the term "machine direction oriented" when
referring to a protuberance on a papermaking fabric or an element
disposed on the surface of a tissue ply or product generally means
that the element or protuberance's principle axis of orientation is
positioned at an angle of less than about 20 degrees relative to
the machine direction (MD) axis of the fabric or tissue sheet.
[0030] As used herein the term "cross-machine direction oriented"
when referring to a protuberance on a papermaking fabric or an
element disposed on the surface of a tissue ply or product
generally means that the element or protuberance's principle axis
of orientation is positioned at an angle of greater than about 20
degrees relative to the machine direction (MD) axis of the fabric
or tissue sheet. For example, a discrete, nonwoven protuberance
disposed on the web contacting surface of a papermaking fabric
having an element angle greater than 20 degrees, such as from 20 to
about 40 degrees, may be said to be cross-machine direction
oriented.
[0031] As used herein, the term "protuberance" generally refers to
a three-dimensional element disposed on the web contacting surface
of a papermaking fabric. For example, in one embodiment, a
protuberance may be formed by one or more warp filaments overlaying
a plurality of shute filaments. In other instances a protuberance
may be a nonwoven material disposed on the web contacting surface
of the fabric.
[0032] As used herein, the term "valley" generally refers to a
portion of a papermaking fabric or a tissue sheet that lies below
the uppermost surface plane of the fabric or sheet and is generally
bounded by a pair of protuberances in the case of a fabric valley,
or a pair of elements, in the case of a sheet valley.
[0033] As used herein, the "valley bottom" generally refers to the
lowest surface plane of a fabric or a tissue sheet. The valley
bottom of a papermaking fabric is generally defined by the top of
the lowest visible filament which a tissue web can contact when
molding into the textured fabric and may be a warp knuckle, a shute
knuckle, or both. The "valley bottom plane" is the z-direction
plane intersecting the top of the elements comprising the valley
bottom.
[0034] As used herein, the term "valley depth" when referring to a
valley of a papermaking fabric generally refers to z-directional
depth of a given valley. Papermaking fabrics prepared according to
the present invention may have relatively deep valleys, such as
valleys having valley depths greater than about 0.30 mm, more
preferably greater than about 0.35 mm and still more preferably
greater than about 0.40 mm, such as from about 0.30 to about 1.0
mm. Valley depth of a fabric may be measured by profilometry as the
difference between C2 (95 percentile height) and C1 (5 percentile
height) values, having units of millimeters (mm). In certain
instances valley depth may be referred to as S90. To determine
valley depth a profilometry scan of a fabric is generated as
described herein, from which a histogram of the measured heights is
generated, and an S90 value (95 percentile height (C2) minus the 5
percentile height (C1), expressed in units of mm) is
calculated.
[0035] As used herein, the term "valley width" when referring to a
valley of a papermaking fabric generally refers to the width of a
valley disposed on a fabric according to the present invention.
Generally valley width is measured along a line drawn normal to the
machine direction axis of the fabric that intersects at least two
adjacent MD oriented protuberances. The valley width of a given
fabric may vary depending on the weave pattern, however, in certain
instances the valley width may be greater than about 1.0 mm, more
preferably greater than about 1.5 mm and still more preferably
greater than about 2.0 mm, such as from about 2.0 to about 5.0
mm.
[0036] As used herein, the term "element angle" when referring to a
protuberance disposed on the web contacting surface of a
papermaking fabric or an element disposed on the air side of a
tissue sheet is the orientation of the protuberance or element
along its longitudinal axis relative to the MD axis of the fabric
or tissue sheet. The element angle of a papermaking fabric
protuberance may be measured by profilometry and described in the
Test Method section below, or alternatively by microscopy as
described in the Test Method section below. The element angle of an
element disposed on a tissue sheet is preferably measured by
microscopy as described in the Test Method section below.
[0037] As used herein, the term "caliper" is the representative
thickness of a single sheet (caliper of tissue products comprising
one or more plies is the thickness of a single sheet of tissue
product comprising all plies) measured in accordance with TAPPI
test method T402 using a ProGage 500 Thickness Tester
(Thwing-Albert Instrument Company, West Berlin, N.J.). The
micrometer has an anvil diameter of 2.22 inches (56.4 mm) and an
anvil pressure of 132 grams per square inch (per 6.45 square
centimeters) (2.0 kPa).
[0038] As used herein, the term "sheet bulk" refers to the quotient
of the caliper (.mu.m) divided by the bone dry basis weight
generally expressed as grams per square meter (gsm). The resulting
sheet bulk is expressed in cubic centimeters per gram (cc/g).
Tissue products prepared according to the present invention may, in
certain embodiments, have a sheet bulk greater than about 12 cc/g,
more preferably greater than about 15 cc/g and still more
preferably greater than about 17 cc/g.
[0039] As used herein, the term "roll bulk" refers to the volume of
paper divided by its mass on the wound roll. Roll Bulk is
calculated by multiplying pi (3.142) by the quantity obtained by
calculating the difference of the roll diameter squared (having
units of centimeters squared) and the outer core diameter squared
(having units of centimeters squared) divided by 4, divided by the
quantity sheet length (having units of centimeters) multiplied by
the sheet count multiplied by the bone dry basis weight of the
sheet (having units of grams per square meter).
[0040] As used herein, the term "roll firmness" or simply
"firmness" generally refers to Kershaw Firmness, which is measured
using the Kershaw Test as described in detail in U.S. Pat. No.
6,077,590, which is incorporated herein by reference in a manner
consistent with the present disclosure. The apparatus is available
from Kershaw Instrumentation, Inc. (Swedesboro, N.J.) and is known
as a Model RDT-2002 Roll Density Tester.
[0041] As used herein, the term "roll structure" generally refers
to the overall appearance and quality of a rolled tissue product
and is the product of roll bulk (having units of cc/g) and caliper
(having units of cm) divided by Firmness (having units of cm). Roll
structure is generally referred to herein without reference to
units.
[0042] As used herein, the term "slope" refers to slope of the line
resulting from plotting tensile versus stretch and is an output of
the MTS TestWorks.TM. in the course of determining the tensile
strength as described in the Test Methods section herein. Slope is
reported in the units of grams (g) per unit of sample width
(inches) and is measured as the gradient of the least-squares line
fitted to the load-corrected strain points falling between a
specimen-generated force of 70 to 157 grams (0.687 to 1.540 N)
divided by the specimen width.
[0043] As used herein, the term "geometric mean slope" (GM Slope)
generally refers to the square root of the product of machine
direction slope and cross-machine direction slope. While the GM
Slope may vary amongst tissue products prepared according to the
present disclosure, however, in certain instances paper towel
products may have a GMT greater than about 1,500 g/3'' and a GM
Slope less than about 14,000 g, more preferably less than about
13,000 g and still more preferably less than about 12,000 g, such
as from about 7,000 to about 14,000 g. In other instances, bath
tissue products may have a GMT less than about 1,000 g/3'' and a GM
Slope less than about 8,000 g, more preferably less than about
7,000 g and still more preferably less than about 6,000 g, such as
from about 4,000 to about 8,000 g.
[0044] As used herein, the term "geometric mean tensile" (GMT)
refers to the square root of the product of the machine direction
tensile strength and the cross-machine direction tensile strength
of the web. While the GMT may vary, paper towel products prepared
according to the present disclosure may, in certain embodiments,
have a GMT greater than about 1,500 g/3'', and more preferably
greater than about 1,750 g/3'' and still more preferably greater
than about 2,000 g/3'', such as from about 1,500 to about 4,000
g/3'', such as from about 2,000 to about 3,500 g/3''. In other
instances bath tissue products prepared according to the present
disclosure may have a GMT less than about 1,000 g/3'', such as from
about 500 to about 1,000 g/3''.
[0045] As used herein, the term "stiffness index" refers to the
quotient of the geometric mean tensile slope, defined as the square
root of the product of the MD and CD slopes (typically having units
of kg), divided by the geometric mean tensile strength (typically
having units of grams per three inches).
Stiffness Index = MD Tensile Slope ( kg ) .times. CD Tensile Slope
( kg ) GMT ( g / 3 '' ) .times. 1 , 000 ##EQU00001##
While the Stiffness Index may vary, tissue products prepared
according to the present disclosure may, in certain embodiments,
have a Stiffness Index less than about 10.0, more preferably less
than about 8.0. In certain instances single ply paper towel
products prepared according to the present invention may have a GMT
from about 1,500 to about 2,500 g/3'' and a Stiffness Index from
about 3.5 to about 5.0. In other instances multi-ply paper towel
products prepared according to the present invention may have a GMT
from about 2,000 to about 3,500 g/3'' and a Stiffness Index from
about 3.5 to about 5.0. In still other instances bath tissue
products prepared according to the present invention may have a GMT
less than about 1,000 g/3'' and a Stiffness Index from about 5.0 to
about 8.0.
[0046] As used herein the term "tensile ratio" generally refers to
the ratio of machine direction (MD) tensile (having units of g/3'')
and the cross-machine direction (CD) tensile (having units of
g/3''). While the Tensile Ratio may vary, tissue products prepared
according to the present disclosure may, in certain embodiments,
have a Tensile Ratio less than about 2.5, such as from about 1.0 to
about 2.5, such as from about 1.2 to about 2.0.
[0047] As used herein the term "discrete" when referring to an
element disposed on a tissue sheet or papermaking fabric generally
means that the element is visually unconnected from other elements
and does not extend continuously in any dimension of the
papermaking fabric or tissue sheet surface.
[0048] As used herein, the term "uninterrupted" generally refers to
a protuberance having an upper surface plane that extends without
interruptions and remains above the valley bottom plane for the
length of the protuberance. Undulations of the upper surface plane
within a protuberance along its length such as those resulting from
twisting of warp filaments or warp filaments forming the
protuberance tucking under one another are not considered to be
interruptions.
[0049] As used herein the term "background pattern" refers to a
pattern that substantially covers the surface of a tissue product.
One of skill in the art may appreciate that a background pattern
may be distinguished from a repeating pattern because a repeating
pattern may comprise a plurality of line segment patterns, line
segment axes, and cells whereas, in some embodiments, a background
pattern may only comprise a single feature which is repeated at any
frequency and/or interval. In other embodiments, a background
pattern comprises a plurality of features which may form a
repeating unit. A repeating unit may be described as a design
comprising a plurality of one or more base patterns.
[0050] As used herein the term "embossed" when referring to a
tissue product means that during the manufacturing process one or
more of the tissue plies that make up the product have been
subjected to a process which converts a smooth surfaced tissue web
to a decorative surface by replicating an embossing pattern on one
or more embossing rolls, which form a nip through which the tissue
web passes. Embossed does not include wet molding, creping,
microcreping, printing or other processes that may impart a texture
and/or decorative pattern to a tissue web.
DETAILED DESCRIPTION
[0051] The present inventors have now surprisingly discovered that
certain woven papermaking fabrics, and in particular woven transfer
and through-air drying (TAD) fabrics, having a first plurality of
protuberances oriented in the machine direction (MD) and a second
plurality protuberances oriented in the cross-machine direction
(CD) may be used to produce tissue webs and products having high
bulk and visually appealing aesthetics without compromising
operating efficiency. For example, in certain embodiments, the
present invention provides a papermaking fabric having a machine
contacting surface and an opposite web contacting surface, the web
contacting surface comprising a plurality of spaced apart MD
oriented protuberances and a plurality of CD oriented protuberances
disposed thereon, where the CD oriented protuberances are discrete
and comprise less than about 15 percent of the surface area of the
web contacting surface of the fabric and more preferably less than
about 10 percent, and still more preferably less than about 8
percent, such as from about 2 to about 10 percent, such as from
about 2 to about 8 percent, such as from about 2 to about 5
percent.
[0052] Despite comprising a relatively small amount of the surface
area of the web contacting surface, the CD oriented protuberances
have a significant effect on the physical properties of tissue
sheets and products manufactured using the instant fabrics--such as
improving sheet bulk and enabling the winding of spirally wound
rolls having high roll bulk and good firmness. Additionally, the
inventive papermaking fabrics are well suited for the manufacture
of both paper towel and bath tissue products having good roll bulk
and firmness. For example, the fabric may be used to produce a
rolled bath tissue product having a basis weight less about 50
grams per square meter (gsm), a geometric mean tensile (GMT)
strength less than about 1,000 g/3'', a caliper of at least about
350 .mu.m and a roll structure of about 0.75 greater and more
preferably about 1.0 or greater. In other instances the fabric may
be used to produce a rolled paper towel product having a basis
weight greater than about 35 gsm, a GMT greater than about 1,500
g/3'', a caliper of about 700 .mu.m or greater and a roll structure
of about 1.5 or greater and more preferably about 1.75 or
greater.
[0053] Accordingly, the instant papermaking fabrics may be used in
the manufacture of a broad range of paper products, particularly
wet-laid tissue webs and more particularly, wet-laid tissue
products such as bath tissues, facial tissues, paper towels,
industrial wipers, foodservice wipers, napkins, and other similar
products. Further, the inventive fabrics are well suited for use in
a wide variety of tissue manufacturing processes. For example, the
fabrics may be used as TAD fabrics in either uncreped or creped
applications to generate aesthetically acceptable patterns and
good, bulky tissue product attributes. Alternatively, the fabrics
may be used as impression fabrics in wet-pressed papermaking
processes.
[0054] In certain embodiments the fabrics comprise a support
structure formed from interweaving shute and warp filaments.
Depending on the intended application of the papermaking fabrics,
the shute count may be from about 10 to about 80 ends per inch,
more preferably from about 20 to about 60 ends per inch, and still
more preferably from about 25 to about 40 ends per inch. Warp
filaments useful in weaving the fabrics may have a diameter from
about 0.2 to about 0.7 mm, such as from about 0.3 to about 0.5
mm.
[0055] The woven support structure preferably comprises a plurality
of MD oriented protuberances, which may be continuous or discrete.
In a particularly preferred embodiment the MD oriented
protuberances are continuous and have a width of from about 0.2 to
about 2.5 mm, such as from about 0.5 to about 2.0 mm and the
frequency of occurrence of the MD oriented protuberances in the
cross-machine direction of the fabric is from about 0.5 to about 8
per centimeter, such as from about 3.2 to about 7.9 per centimeter,
such as from about 4.2 to about 5.3 per centimeter.
[0056] In those instances where the MD oriented protuberances are
formed by interweaving shute and warp filaments, the protuberances
may have a height, generally measured as the z-directional length
between the uppermost surface of a warp filament forming the
protuberance and the valley bottom plane, from about 250 to about
350 percent of the diameter of the warp strand forming the
protuberance, such as from about 260 to about 300 percent of the
warp strand diameter. In other instances, where warp strands of
multiple diameters are used to weave the protuberance, the height
may be from about 105 to about 125 percent of the weighted-average
shute diameters.
[0057] The MD oriented protuberances may be substantially aligned
with the MD axis of the fabric or they may have a non-zero element
angle. For example, the warp filaments may be woven to form
protuberances extending in a continuous manner across the fabric
and slightly skewed relative to the MD axis of the fabric. In this
manner the MD oriented protuberances may have a non-zero element
angle, such as an element angle from about 0.5 to 20 degrees, such
as from about 2 to about 15 degrees, and more preferably from about
2 to about 10 degrees. In a particularly preferred embodiment the
web contacting surface of the fabric comprises a plurality of
spaced apart, parallel, MD oriented protuberances having an element
angle from about 2 to about 10 degrees.
[0058] In certain embodiments the MD oriented protuberances may be
arranged in a continuous pattern, extending from a first lateral
edge of the fabric to a second lateral edge, in which adjacent
protuberances are generally parallel to one another and equally
spaced apart. Between adjacent protuberances are valleys having
sidewalls formed by the protuberances. In this manner, the valleys,
like the protuberances, may be oriented at an angle relative to the
MD axis of the fabric.
[0059] Papermaking fabrics having woven MD oriented protuberances
suitable for use in the present invention may be prepared as
described in U.S. Pat. Nos. 6,998,024 and 7,611,607, the contents
of which are incorporated herein in a manner consistent with the
present disclosure. In a particularly preferred embodiment the MD
oriented protuberances may be substantially continuous and woven
from two or more warp filaments grouped together and supported by
multiple shute strands of two or more diameters as disclosed in
U.S. Pat. No. 7,611,607. MD protuberances woven in this manner can
be oriented at an angle of from 0 to about 15 degrees relative to
the true machine direction of the fabric.
[0060] The MD oriented protuberances can be configured
substantially the same in terms of any one or more characteristics
of height, width, length or element angle. For example, in certain
embodiments, substantially all the MD oriented protuberances have
substantially similar characteristics of height, width and element
angle. In other embodiments however, the MD oriented protuberances
may be configured such that one or more characteristics of height,
width, or length of the protuberances vary from one MD oriented
protuberance to another MD oriented protuberance.
[0061] The fabric further comprises a plurality of second
protuberances, which are generally oriented in the cross-machine
direction and are preferably discrete. In particularly preferred
embodiments the CD oriented protuberances are formed by topically
applying a polymeric material to the woven support structure.
Suitable methods of topical application include printing and
extruding polymeric material onto the surface of the woven support
structure. Particularly suitable polymeric materials include
materials that can be strongly adhered to the woven support
structure and are resistant to thermal degradation at typical
tissue machine dryer operating conditions and are reasonably
flexible, such as silicones, polyesters, polyurethanes, epoxies,
polyphenylsulfides and polyetherketones.
[0062] In other embodiments the CD oriented protuberances may be
formed by extruding a polymeric strand onto a woven support
structure, such as that described in U.S. Pat. No. 6,398,910, the
contents of which are incorporated herein in a manner consistent
with the present discourse. In such embodiments the polymeric
strand is applied so as to form a raised CD oriented protuberance
above the upper most plane of the woven support structure.
[0063] Alternative methods of forming the CD oriented protuberances
include applying cast or cured films, weaving, embroidering or
stitching polymeric fibers into the surface.
[0064] The CD oriented protuberances may be arranged on the web
contacting surface of the fabric in a pattern. Suitable patterns
useful in the present invention are illustrated in FIGS. 5A-5C. For
example, with reference to FIG. 5A, the CD oriented protuberances
may be discrete and occur in a regular, repeating pattern
comprising pairs of protuberance, such as first pair of
protuberances and second pair of protuberances, spaced apart from
one another in the cross-machine direction (D1) at least about 5.0
mm and more preferably at least about 10.0 mm. Within a given pair
of protuberances, the protuberances may be spaced apart a distance
(D2) from about 2.0 to about 6.0 mm, such as from about 2.0 to
about 5.0 mm.
[0065] In other embodiments the CD oriented protuberances may be
arranged in a pattern such that each CD oriented protuberance
contacts, and more preferably traverses, at least one MD oriented
protuberance and in certain instances two or more adjacent MD
oriented protuberances. In those embodiments where a CD
protuberance contacts adjacent MD oriented protuberances, the CD
protuberance may extend across the entire width of a valley and
form a valley endwall.
[0066] With continued reference to FIG. 5A, pairs of CD oriented
protuberances may be spaced apart from other pairs of protuberances
in the machine direction a distance (D3) from about 3.0 to about
10.0 mm, such as from about 4.0 to about 6.0 mm. Further, the pair
of CD oriented protuberances may be arranged parallel to one
another and have an element angle from about 20 to about 45 degrees
and more preferably from about 25 to about 40 degrees.
[0067] Regardless of the whether the CD oriented protuberances are
arranged in a pattern or are randomly distributed on the web
contacting surface of the fabric, the percentage the web contacting
surface that is covered by CD oriented protuberances is generally
less than about 15 percent of the surface area of the web
contacting surface of the fabric and more preferably less than
about 10 percent, and still more preferably less than about 8
percent, such as from about 2 to about 10 percent, such as from
about 2 to about 8 percent, such as from about 2 to about 5
percent.
[0068] In certain preferred embodiments the CD oriented
protuberances comprise a polymeric material disposed on the woven
support structure such that the upper surface of the CD oriented
protuberance lies above the surface of the upper most filament of
the woven support structure. In this manner the CD oriented
protuberance may form the upper most surface plane of the
papermaking fabric and may have a height, generally measured from
the valley bottom plane, greater than about 1,000 .mu.m, such as
from about 1,000 to about 2,000 .mu.m. In other instances the upper
most surface of the woven portion of the fabric may have a height
from about 500 to about 1,000 .mu.m and the upper most surface of
the CD oriented protuberance may have a height from about 1,000 to
about 2,000 .mu.m.
[0069] With reference now to FIG. 1, one embodiment of a
papermaking fabric 10 according to the present invention is
illustrated. The fabric 10 has two principal dimensions--a machine
direction (MD), which is the direction within the plane of the
fabric 10 parallel to the principal direction of travel of the
tissue web during manufacture, and a cross-machine direction (CD),
which is generally orthogonal to the machine direction. The
papermaking fabric 10 generally comprises a woven support structure
consisting of filaments such as a plurality of warp filaments and a
plurality of shute filaments woven together to form a machine
contacting surface and a web contacting surface 20.
[0070] With continued reference to FIG. 1, the web contacting
surface 20 of the fabric 10 comprises a plurality of MD oriented
protuberances 22 and a plurality of CD oriented protuberances 38.
The protuberances 22, 38 are generally disposed on the web
contacting surface 20 for cooperating with, and structuring of, the
wet fibrous web during manufacturing. In certain embodiments the CD
oriented elements 38 may be disposed on the web contacting surface
20 in a pattern comprising a repeating motif 40 of first and second
CD oriented protuberances 38a, 38b having substantially similar
shape and size and arranged in a pair wise fashion with similar
element angles. The element angle of the CD oriented protuberance
(.beta.), which is generally measured as the angle between the MD
axis 27 and the longitudinal axis 29 of the protuberance 38 may
range from about 20 to about 40 degrees, such as from about 25 to
about 35 degrees.
[0071] Regardless of whether the CD oriented protuberances 38 are
disposed in a pattern or are randomly disposed on the web
contacting surface 20, the protuberances 38 generally comprise less
than about 15 percent of the web contacting surface 20 of the
fabric 10 and more preferably less than about 10 percent, and still
more preferably less than about 8 percent, such as from about 2 to
about 10 percent, such as from about 2 to about 8 percent, such as
from about 2 to about 5 percent of the web contacting surface 20 of
the fabric 10.
[0072] The MD oriented protuberances 22 may extend generally in a
first direction along a major axis 25 across one dimension of the
fabric 10 in a continuous fashion. In this manner a protuberance 22
may extend from a first lateral edge 17 to a second lateral edge
19. In such embodiments the length of the protuberance is dependent
upon the length of the fabric 10 and the angle of the protuberance
relative to the machine direction (MD). For example, the
protuberances 22 may be arranged in a parallel fashion and extend
along a major axis 25 at an angle (.alpha.) relative to the machine
direction axis 27. In this manner the protuberances 22 generally
have a long direction axis, i.e., the major axis 25, that
intersects the machine direction axis 27 to form an element angle
(.alpha.), which may be greater than about 0.5 degrees, such as
from about 2.0 to about 15.0 degrees, such as from about 5.0 to
about 10.0 degrees. While the MD oriented protuberances 22
illustrated in FIG. 1 are arranged in a parallel fashion and have
the same element angle (.alpha.), the invention is not so limited.
In other embodiments the element angle may vary amongst the MD
oriented protuberances and in still other embodiments the MD
oriented protuberances may intersect one another.
[0073] With continued reference to FIG. 1, the web contacting
surface 20 may comprise a plurality of valleys 24, which are
generally bounded by adjacent MD oriented protuberances 22 and are
coextensive with the upper surface plane of the fabric 10. With
reference to valley 24a, the valley is discrete and bounded on four
sides by protuberances 22a, 22b and 38c, 38d. In this manner the
valley 24a has the shape of a parallelogram with endwalls formed by
a pair of spaced apart CD oriented protuberances 38c, 38d and
sidewalls formed by a pair of spaced apart MD oriented
protuberances 22a, 22b. The valleys 24 are generally permeable to
liquids and allow water to be removed from the cellulosic tissue
web by the application of differential fluid pressure, by
evaporative mechanisms, or both when drying air passes through the
embryonic tissue web while on the papermaking fabric 10 or a vacuum
is applied through the fabric 10. Without being bound by any
particularly theory, it is believed that the arrangement of
protuberances and valleys allow the molding of the embryonic web
causing fibers to deflect in the z-direction and generate the
caliper of, and patterns on the resulting tissue web.
[0074] With reference now to FIG. 2 the fabric 10 may comprise a
woven support structure 12 comprising interwoven shute and warp
filaments 14, 16. The filaments may be interwoven such that the MD
oriented protuberances 22 is formed by a pair of warp filaments
14a, 14b. The fabric 10 may further comprise a plurality of CD
oriented protuberances, such as CD oriented protuberance 38a, 38b,
which may be formed by printing a polymeric material onto the
support structure 12 such that the protuberance 38a, 38b lie above
the warp filaments 14 and span a pair of spaced apart MD oriented
protuberances, such as protuberances 22a and 22b.
[0075] The fabric 10 may further comprise a plurality of valleys 24
bounded by spaced apart MD oriented protuberances 22a, 22b. The
valleys may, in certain instances be further bound by spaced apart
CD oriented protuberances to provide the fabric with discrete
valleys. For example, as illustrated in FIG. 2, one end of the
valley 24 is bound by CD oriented protuberance 38a, which spans a
pair of spaced apart MD oriented protuberances 22a, 22b.
[0076] The shape of the MD protuberances, such as the height, width
and cross-sectional shape, may vary depending on the size, shape
and number of warp filaments that make up the protuberance. For
example a pair of warp filaments may be bundled together to form a
protuberance, which in certain instances may have a semi-circular
cross-sectional shape. Further, the upper surface of the warp
filaments lie in an upper surface plane above the valley bottom
plane in the z-direction providing the woven MD oriented
protuberance with a height. In certain instances the height of the
protuberances may be altered by selecting warp filaments of
different sizes and shapes and by the number of warps forming a
given protuberance.
[0077] The MD oriented protuberance height may range from about 0.1
to about 5.0 mm, more preferably from about 0.2 to about 3.0 mm, or
even more preferably from about 0.5 to about 1.5 mm. Of course, it
is contemplated that the height can be outside of this preferred
range in some embodiments. Further, while the height of the
protuberances is generally illustrated herein as being
substantially uniform amongst the protuberances, the invention is
not so limited and the protuberances may have different
heights.
[0078] The MD oriented protuberance width may also vary depending
on the construction of the fabric and its intended use. For
example, the width of the protuberances may be influenced by the
number of warp filaments used to form the MD oriented protuberance,
as well as the diameter of the filament used for a given warp
float. In certain embodiments a protuberance may comprise from 2 to
8, such as 4 to 6, warp filaments. In other instances the warp
filaments may have a diameter from about 0.2 to about 0.7 mm, such
as from about 0.3 to about 0.5 mm and the protuberances may be
woven from 2 to 6 adjacent warp filaments.
[0079] With reference again to FIG. 2, the CD protuberances 38a,
38b may be formed from a polymeric material printed on the woven
support structure 12 and may be disposed between a pair of adjacent
MD protuberances 22a, 22b. In other instances the CD protuberances
may traverses at least one MD oriented protuberance. The CD
protuberance may have a length, measured along the long axis of the
protuberance, of from about 2.0 to about 15.0 mm, such as from
about 3.0 to about 10.0 mm, and more preferably from about 5.0 to
about 8.0 mm. In certain embodiments all of the CD protuberances
disposed on the web contacting surface of the sheet are discrete
and have a substantially similar length, such as a length from
about 3.0 to about 10.0 mm, and more preferably from about 5.0 to
about 8.0 mm. Further, the CD protuberance may have a width,
generally measured at the widest point of the protuberance normal
to the longest axis of the protuberance, from about 600 to about
1,500 .mu.m, such as from about 800 to about 1,200 .mu.m.
[0080] The spacing and arrangement of protuberances may vary
depending on the desired tissue product properties and appearance.
If the individual protuberances are too high, or the valley area is
too small, the resulting sheet may have excessive pinholes and
insufficient compression resistance and be of poor quality.
Further, tensile strength may be degraded if the span between
adjacent MD protuberances greatly exceeds the fiber length.
Conversely, if the spacing between adjacent MD protuberances is too
small the tissue will not mold completely into the fabric
negatively affecting important sheet properties such as sheet
caliper and cross-machine direction properties such as stretch and
tensile energy absorption.
[0081] In particularly preferred embodiments the invention provides
a papermaking fabric having a machine contacting surface and an
opposite web contacting surface, wherein the web contacting surface
comprises a plurality of MD oriented protuberances extending
continuously throughout one dimension of the fabric and each of the
plurality of MD protuberances are spaced apart from one another.
Thus, the MD oriented protuberances may be spaced apart across the
entire cross-machine direction of the fabric or may run diagonally
relative to the machine direction and have an element angle from
about 2 to about 10 degrees. Further the MD oriented protuberances
may all be similarly shaped and sized. The web contacting surface
further comprises a plurality of substantially CD oriented
protuberances, where the CD protuberances are discrete and contact
at least one MD oriented protuberance and have a length from about
3.0 to about 10.0 mm and have an element angle greater than about
20 degrees, such as from about 20 to about 40 degrees and more
preferably from about 25 to about 35 degrees.
[0082] The MD oriented protuberances generally define valleys there
between. The valleys are preferably air and liquid permeable and
have an upper surface that defines the lowest web contacting
surface of the fabric. Depending on the shape and size of the MD
oriented protuberances, the valley depths may vary, such as about
0.30 mm or greater, such as from about 0.30 to about 2.00 mm, such
as from about 0.50 to about 1.50 mm. In certain instances at least
a portion of the valleys may be further bound by CD oriented
protuberances, which may span a pair of adjacent MD oriented
protuberances and form the valley endwalls. In such instances a
portion of the valleys may be discrete, having sidewalls defined by
the spaced part MD oriented protuberances and endwalls defined by
spaced apart CD oriented protuberances. The discrete valleys may
have a length of about 10 mm or greater, such as about 15 mm or
greater, such as about 20 mm or greater, such as from about 10 to
about 30 mm, such as from about 15 to about 30 mm, such as from
about 20 to about 30 mm.
[0083] In certain embodiments the fabric may comprise a web
contacting surface having a plurality of substantially similarly
shaped valleys having first and second sidewalls formed by MD
oriented protuberances and first and second endwalls formed by CD
oriented protuberances where the valleys have a length of about 10
mm or greater, such as about 15 mm or greater, such as about 20 mm
or greater, such as from about 10 to about 30 mm, such as from
about 15 to about 30 mm, such as from about 20 to about 30 mm.
[0084] Several exemplary papermaking fabrics are illustrated in the
attached figures. The illustrated fabrics are woven so as to form a
plurality of MD oriented protuberances and have nonwoven CD
oriented protuberances, which in certain instances define discrete
valleys there between. The illustrated fabrics generally have
valley depths greater than about 0.30 mm, such as from about 0.30
to about 2.00 mm, such as from about 0.50 to about 1.50 mm. For
example, as illustrated in the profilometry scan of FIG. 4, the
valleys generally form the lowest most portion of the web
contacting surface of the fabric and are bounded by woven MD
oriented protuberances and nonwoven CD oriented protuberances. The
valleys have a depth of about 1.0 mm and the nonwoven CD oriented
protuberances form the upper most portion of the web contacting
surface.
[0085] The CD oriented protuberances may be disposed on the fabric
in any number of different patterns. Three exemplary CD oriented
protuberance patterns are illustrated in FIGS. 5A-5C. The patterns
may be arranged such that the CD oriented protuberances cover less
than about 15 percent of the web contacting surface 20 of the
fabric 10 and more preferably less than about 10 percent, and still
more preferably less than about 8 percent, such as from about 2 to
about 10 percent, such as from about 2 to about 8 percent, such as
from about 2 to about 5 percent of the web contacting surface 20 of
the fabric 10. The pattern may further comprise substantially
similarly shaped and sized CD oriented protuberances that have
similar element angles, which are generally greater than about 20
degrees. The CD oriented protuberances may all have substantially
similar element angles or the angles may be varied amongst the
protuberances.
[0086] The inventive papermaking fabrics disclosed herein may be
useful in a number of tissue manufacturing processes. In
particularly preferred embodiments the fabrics are useful as
through-air drying fabrics where the web contacting surface
three-dimensional topography facilitates the molding and
structuring of the nascent tissue web during manufacture. The
molding and structuring of the web during manufacture may impart
three-dimensionality to the resulting tissue sheet or ply. In
certain instances the three-dimensionality imparted to the
resulting sheet or ply affects the physical properties of the
finished tissue product, such as sheet bulk, stretch, and tensile
energy absorption. For example, the finished product may comprise a
plurality of substantially machine direction (MD) oriented ridges
that may be pulled out when the product is subjected to strain in
the cross-machine direction (CD) resulting in increased CD stretch
and tensile energy absorption.
[0087] In a particularly preferred embodiment one or more of the
tissue plies may be manufactured by a through-air dried process
using the inventive fabric disclosed herein. In such processes the
embryonic web is noncompressively dried. For example, tissue plies
useful in the present invention may be formed by either creped or
uncreped through-air dried processes. Particularly preferred are
uncreped through-air dried webs, such as those described in U.S.
Pat. No. 5,779,860, the contents of which are incorporated herein
in a manner consistent with the present disclosure.
[0088] In other embodiments one or more of the tissue plies may be
manufactured by a process including the step of using pressure,
vacuum, or air flow through the wet web (or a combination of these)
to conform the wet web into a shaped fabric and subsequently drying
the shaped sheet using a Yankee dryer, or series of steam heated
dryers, or some other means, including but not limited to tissue
made using the ATMOS process developed by Voith or the NTT process
developed by Metso; or fabric creped tissue, made using a process
including the step of transferring the wet web from a carrying
surface (belt, fabric, felt, or roll) moving at one speed to a
fabric moving at a slower speed (at least 5 percent slower) and
subsequently drying the sheet. Those skilled in the art will
recognize that these processes are not mutually exclusive, e.g., an
uncreped TAD process may include a fabric crepe step in the
process.
[0089] Accordingly, in addition to providing inventive papermaking
fabrics, the present invention provides novel tissue products,
which may comprise one, two or more plies that are manufactured
using the same or different tissue making techniques. In one
embodiment the invention provides a single ply tissue product
having a basis weight greater than about 20 gsm, such as from about
20 to about 60 gsm, such as from about 35 to about 55 gsm, such as
from about 35 to about 45 gsm. In other embodiments the present
invention provides multi-ply tissue products having a basis weight
greater than about 20 gsm, such as from about 20 to about 60 gsm,
such as from about 35 to about 55 gsm.
[0090] In particularly preferred embodiments the tissue products of
the present invention are produced using a noncompressive drying
method which tends to preserve, or increase, the caliper or
thickness of the wet web including, without limitation, through-air
drying, infra-red radiation, microwave drying, etc. Because of its
commercial availability and practicality, through-air drying is
well-known and is a preferred means for noncompressively drying the
web for purposes of this invention. The through-air drying process
and tackle can be conventional as is well known in the papermaking
industry. In certain instances it may be preferable to use a
through-air drying fabric having a web contacting surface with
three-dimensional topography as described above. After manufacture
the web may be subsequently converted, as is well known in the art,
by processes such as calendering, embossing, printing, lotion
treating, slitting, cutting, folding, and packaging. Particularly
preferred are processes that apply a plurality of embossments to at
least one surface of the tissue web, as will be discussed in more
detail below. Multi-ply products may be combined using well known
techniques. In certain preferred embodiments the plies may be
combined by a glue laminating embossing process which provides the
tissue product with an embossing pattern on at least one of its
outer surfaces.
[0091] In one embodiment of the present invention, the tissue
product has a plurality of embossments. In one embodiment the
embossment pattern is applied only to the first ply, and therefore,
each of the two plies serve different objectives and are visually
distinguishable. For instance, the embossment pattern on the first
ply provides, among other things, improved aesthetics regarding
thickness and quilted appearance, while the second ply, being
unembossed, is devised to enhance functional qualities such as
absorbency, thickness and strength. In another embodiment the
fibrous structure product is a two-ply product wherein both plies
comprise a plurality of embossments. Suitable means of embossing
include, for example, those disclosed in U.S. Pat. Nos. 5,096,527,
5,667,619, 6,032,712 and 6,755,928.
[0092] One exemplary tissue product prepared according to the
present invention is illustrated in FIGS. 6 and 7. As illustrated
in FIGS. 6 and 7, which are images of the air side 210 of an
inventive tissue product 100, the MD oriented elements 220 are
spaced apart from one another and define a plurality of valleys 240
there between. The MD oriented elements 220 are elevated above the
valleys 240 and are substantially continuous. The valleys 220
generally define the lowest surface of the product 100 and, in
certain instances, are discontinuous. The valley discontinuities
are formed by CD oriented elements 380, which together with the MD
oriented elements 220 form the upper most surfaces of the tissue
sheet.
[0093] At least a portion of the CD oriented elements span adjacent
MD oriented elements to form valley endwalls and define the valley
length, which is generally greater than about 10 mm, such as about
15 mm or greater, such as about 20 mm or greater, such as from
about 10 to about 30 mm. One skilled in the art will appreciate
that depending on the pattern of CD oriented elements, the valley
lengths within a given tissue sheet may vary and an inventive
tissue sheet may have valleys which are continuous or are
discontinuous and certain discontinuous valleys may have a length
outside of the preferred range.
[0094] With reference now to FIGS. 8A-8C the height of the MD and
CD oriented elements relative to the valleys is further
illustrated. The MD and CD oriented elements may form the upper
surface plane of the tissue sheet and the valley bottoms may form
the lowest surface plane. The height difference between the lowest
and uppermost surface planes may vary depending on the properties
of the fabric used to manufacture the tissue sheet, as well as the
basis weight of the tissue sheet and the manufacturing process.
[0095] In certain embodiments, the present invention provides a
towel product comprising a single tissue ply having a basis weight
greater than about 35 gsm and a GMT greater than about 1,500 g/3''
where the air contacting side of the product comprises a valley
having an upper surface lying in a valley bottom plane and MD and
CD oriented elements having upper surfaces lying in an upper tissue
surface plane where the distance between the valley bottom plane
and the upper tissue surface plane is greater than about 500 .mu.m,
such as from about 500 to about 1,200 .mu.m.
[0096] In other embodiments, the present invention provides a bath
tissue product comprising a single tissue ply having a basis weight
less than about 50 gsm and a GMT less than about 1,000 g/3'' where
the air contacting side of the product comprises a valley having an
upper surface lying in a valley bottom plane and MD and CD oriented
elements having upper surfaces lying in an upper tissue surface
plane where the distance between the valley bottom plane and the
upper tissue surface plane is greater than about 300 .mu.m, such as
from about 300 to about 600 .mu.m.
[0097] With reference now to FIGS. 9A-9C the cross-section profile
of an inventive tissue sheet is illustrated along a valley and
further illustrates the valley discontinuity caused by a CD
oriented element. As illustrated in FIG. 9C the CD oriented element
has an upper surface that lies above the valley bottom plane.
Again, the distance between the valley bottom plane and the upper
surface of the CD oriented element may vary depending upon
depending on the properties of the fabric used to manufacture the
tissue sheet, as well as the basis weight of the tissue sheet and
the manufacturing process, but in certain embodiments may range
from about 300 to about 1,200 .mu.m, such as from about 400 to
about 1,000 .mu.m.
[0098] It is believed that by forming a tissue webs using a
papermaking fabric having both MD and CD oriented protuberances,
such as those disclosed herein, that nesting may be reduced when
the webs are converted into rolled product forms. Reduced nesting
may, in-turn, improve certain properties, such as bulk and
firmness, of the rolled product. Typically, nesting arises as a
result of using textured papermaking fabrics, which impart the
tissue web with valleys and ridges. While these ridges and valleys
can provide many benefits to the resulting web, problems sometimes
arise when the web is converted into final product forms. For
example, when webs are converted to rolled products, the ridges and
valleys of one winding are placed on top of corresponding ridges
and valleys of the next winding, which causes the roll to become
more tightly packed, thereby reducing roll bulk, increasing density
and making the winding of the product less consistent and
controllable. Thus, in certain embodiments the present invention
provides tissue products comprising a tissue web having MD and CD
oriented elements, where the CD oriented elements reduce nesting of
the web when it is converted into a rolled product. The resulting
rolls generally have higher roll bulk at a given roll firmness.
Further, the rolls generally have a surprising degree of
interlocking between successive wraps of the spirally wound web,
improving roll structure at a given roll firmness, more
specifically allowing less firm rolls to be made without slippage
between wraps.
[0099] Improving interlocking between successive wraps allows less
firm rolls to be made without slippage between wraps. For example,
compared to tissue products produced using a through-air drying
fabric with an offset seam, such as those disclosed in U.S. Pat.
No. 7,935,409, the contents of which are incorporated herein in a
manner consistent with the present disclosure, rolled tissue
products of the present disclosure have similarly improved roll
structure and reduced nesting. One measure of the reduced nesting
is improved roll structure. Generally rolled tissue products
prepared according to the present invention have a roll structure
greater than about 0.75, more preferably greater than about 1.0,
still more preferably greater than about 1.5. For example, in one
embodiment the invention provides a single ply bath tissue having a
caliper from about 350 to about 550 .mu.m wound into a roll having
a roll structure greater than about 0.75. In another embodiment the
invention provides a single ply paper towel having a caliper from
about 600 to about 900 .mu.m wound into a roll having a roll
structure greater than about 1.5.
[0100] Not only are the inventive papermaking fabrics useful in the
manufacture of tissue webs that may be converted into rolled
products having improved physical properties, the fabrics are also
useful for imparting the web with a relatively basic, yet visually
appealing pattern. Without being bound by any particular theory, it
is believed that by using a fabric having a relatively small degree
of its surface area printed with CD oriented protuberances, the
physical benefits of the CD elements imparted to the finished
product are achieved without an excessive amount of pattern that
may obscure the background pattern imparted by the MD oriented
protuberances or interfere with embossing patterns subsequently
applied to the web.
[0101] Accordingly, the inventive papermaking fabrics are well
suited to the manufacture of a wide range of tissue products, such
as both tissue and towel products, as well as single and multi-ply
products and both embossed and unembossed products. Moreover, the
tissue products produced using the inventive fabrics have several
unique properties, such as an air side having discrete valleys and
discrete CD oriented elements, and physical properties that are
comparable or better than those of the prior art. For instance,
tissue webs may have increased bulk and reduced stiffness compared
to prior art webs. Similarly, rolled products prepared according to
the present disclosure may have improved roll firmness and bulk,
while still maintaining sheet softness and strength properties.
[0102] For example, the present invention provides towel products
having relatively high sheet caliper with a textured air side of
the sheet comprising MD and CD oriented elements and discontinuous
valleys. These improvements translate into rolled products having
desirable physical attributes, as summarized in the table
below.
TABLE-US-00001 TABLE 1 Basis Weight Caliper Sheet Bulk GMT MD
Stretch Firmness Roll Bulk Roll Plies Embossed (gsm) (microns)
(cc/g) (g/3'') (%) (mm) (cc/g) Structure Inventive 1 1 N 36 698
19.6 2079 18.9 6.9 17.8 1.80 Inventive 2 1 N 36 691 19.2 1974 18.7
6.7 17.7 1.83 Inventive 3 1 N 36 706 19.9 2200 17.8 6.6 17.9 1.91
Inventive 4 2 Y 54 1072 19.9 3207 15.7 6.6 17.8 2.89 Inventive 5 2
Y 52 963 18.5 3209 16.4 7 18.5 2.55 Inventive 6 2 Y 52 1095 21 3204
15.9 6.1 18.4 3.30 Viva 1 N 58.4 742 12.7 1416 41.2 4.3 10.8 1.86
Viva Vantage 1 N 54.3 945 17.4 2443 48.9 6.3 14.3 2.14 Scott Towel
1 N 35.6 822 23.1 2432 16.3 6.9 20 2.38 Scott Towel 1 N 35.2 806
22.9 2438 16.3 6.9 19.8 2.31 Bounty 2 Y 50.4 988 19.6 3428 11.2 6
18.7 3.08 Brawny 2 Y 52 837 16.1 3149 10.9 6.9 15.7 1.90 Sparkle 2
Y 47.4 725 15.3 3795 11.7 8.8 16.3 1.34
[0103] In other instances the present invention provides bath
tissue products having good sheet caliper and bulk with a textured
air side of the sheet comprising MD and CD oriented elements and
discontinuous valleys. When spirally wound into a roll, the
resulting products have desirable physical attributes, as
summarized in the table below.
TABLE-US-00002 TABLE 2 Basis Weight Caliper Sheet Bulk GMT MD
Stretch Firmness Roll Bulk Roll Plies Embossed (gsm) (microns)
(cc/g) (g/3'') (%) (mm) (cc/g) Structure Inventive 1 1 N 32.2 505
12.7 655 17.4 6.3 12.73 1.02 Inventive 2 1 N 33.3 475 12.4 662 19.0
6.1 12.34 0.96 Scott Extra Soft 1 N 28.3 386 13.6 756 11.4 7.2 12.0
0.96 Angle Soft 2 Y 37.7 391 10.4 758 19.8 8.9 9.2 1.26 Charmin
Essentials Soft 1 Y 33.3 447 13.4 962 22.3 5.7 13.5 0.78 Charmin
Essentials Strong 1 Y 27.9 312 11.2 1117 27.1 4.1 9.8 2.28
Cottonelle Clean Care 1 N 38.5 483 12.5 1101 16.2 8.4 12.6 2.67
Charmin Ultra Strong 2 Y 37.4 462 12.4 1224 14.9 7.7 12.8 1.65
Quilted Northern Ultra Strong 2 Y 42.6 490 11.5 1286 27.3 7.9 11.7
2.03 Cottonelle Ultra Comfort Care 2 Y 44.4 610 13.7 990 13.2 7.5
12.9 1.90
[0104] Accordingly, in certain embodiments, rolled products made
according to the present disclosure may comprise a spirally wound
tissue web having a roll firmness greater than about 6.0 mm, more
preferably greater than about 6.5 mm and still more preferably
greater than about 7.0 mm, such as from about 6.0 to about 8.0 mm.
Within the above-roll firmness ranges, rolls made according to the
present disclosure do not appear to be overly soft and "mushy" as
may be undesirable by some consumers during some applications.
[0105] In the past, at the above-roll firmness levels, spirally
wound tissue products had a tendency to have low roll bulks and/or
poor sheet softness properties. However, it has now been discovered
that spirally wound tissue products having roll bulks of at least
about 12 cc/g, such as from about 12 to about 18 cc/g, and more
preferably from about 12 to about 15 cc/g may be produced, even
when spirally wound under tension to produce relatively firm rolls,
such as rolls having a roll firmness greater than about 6.0 mm,
more preferably greater than about 6.5 mm and still more preferably
greater than about 7.0 mm, such as from about 6.0 to about 8.0
mm.
Test Methods
Tensile
[0106] The following test methods are to be conducted on samples
that have been in a TAPPI conditioned room at a temperature of
73.4.+-.3.6.degree. F. (about 23.+-.2.degree. C.) and relative
humidity of 50.+-.5 percent for 4 hours prior to the test.
[0107] Tensile testing was done in accordance with TAPPI test
method T-576 "Tensile properties of towel and tissue products
(using constant rate of elongation)" wherein the testing is
conducted on a tensile testing machine maintaining a constant rate
of elongation and the width of each specimen tested is 3 inches.
More specifically, samples for dry tensile strength testing were
prepared by cutting a 3.+-.0.05 inches (76.2 mm.+-.1.3 mm) wide
strip in either the machine direction (MD) or cross-machine
direction (CD) orientation using a JDC Precision Sample Cutter
(Thwing-Albert Instrument Company, Philadelphia, Pa., Model No. JDC
3-10, Serial No. 37333) or equivalent. The instrument used for
measuring tensile strengths was an MTS Systems Sintech 11S, Serial
No. 6233. The data acquisition software was an MTS TestWorks.RTM.
for Windows Ver. 3.10 (MTS Systems Corp., Research Triangle Park,
N.C.). The load cell was selected from either a 50 Newton or 100
Newton maximum, depending on the strength of the sample being
tested, such that the majority of peak load values fall between 10
to 90 percent of the load cell's full scale value. The gauge length
between jaws was 4.+-.0.04 inches (101.6.+-.1 mm) for facial tissue
and towels and 2.+-.0.02 inches (50.8.+-.0.5 mm) for bath tissue.
The crosshead speed was 10.+-.0.4 inches/min (254.+-.1 mm/min), and
the break sensitivity was set at 65 percent. The sample was placed
in the jaws of the instrument, centered both vertically and
horizontally. The test was then started and ended when the specimen
broke. The peak load was recorded as either the "MD tensile
strength" or the "CD tensile strength" of the specimen depending on
the direction of the sample being tested. Ten representative
specimens were tested for each product or sheet and the arithmetic
average of all individual specimen tests was recorded as the
appropriate MD or CD tensile strength of the product or sheet in
units of grams of force per 3 inches of sample. The geometric mean
tensile (GMT) strength was calculated and is expressed as
grams-force per 3 inches of sample width. Tensile energy absorbed
(TEA) and slope are also calculated by the tensile tester. TEA is
reported in units of gmcm/cm.sup.2. Slope is recorded in units of
grams (g) or kilograms (kg). Both TEA and Slope are directionally
dependent and thus MD and CD directions are measured independently.
Geometric mean TEA and geometric mean slope are defined as the
square root of the product of the representative MD and CD values
for the given sample.
Image Analysis
[0108] Tissue products and papermaking fabrics produced according
to the present invention may be analyzed by microscopy as described
herein. Both three-dimensional and two-dimensional images may be
collected and analyzed.
[0109] Three-dimensional surface topography may be analzyed by
generating and analyzing 3D surface maps and cross-sections, such
as those illustrated in FIGS. 5A and 5B. The images are taken using
a VHX-5000 Digital Microscope manufactured by Keyence Corporation
of Osaka, Japan. The microscope is equipped with VHX-5000
Communication Software Ver 1.5.1.1. The lens is an ultra-small,
high performance zoom lens, VH-Z20R/Z20T. Samples to be analyzed
should be undamaged, flat, and include representative CD and MD
oriented elements or protuberances. A sample approximately 4
inches.times.4 inches in size works well.
[0110] A three-dimensional image of the sample is obtained as
follows:
[0111] 1. Turn the digital microscope on, and follow standard
procedures for XY stage Initialization [Auto]
[0112] 2. Turn the microscope magnification to the desired
magnification--100.times. for tissue sheet samples or 20.times. for
papermaking fabrics.
[0113] 3. Place the sample on the stage with the elements or
protuberances facing up toward the lens.
[0114] 4. If the sample does not lie flat, place weights as needed
along the perimeter to make sample lie flat against the stage
surface.
[0115] 5. Use the focus adjustment to bring the sample into sharp
focus.
[0116] 6. Select "Stitching" in the main menu. Select "3D
stitching."
[0117] 7. Set the stitching method by selecting "Stitch around the
current position."
[0118] 8. Select the Z set to set the upper and lower composition
range. The upper limit should be set by going higher than the
highest focal point that is clear. The lower limit should be set by
going lower than the lowest focal point that is clear. After
setting the upper and lower range, click OK.
[0119] 9. Select "Start stitching," to begin acquisition of the
image.
[0120] 10. Select "complete" when the desired area has been imaged,
then "Confirm stitching results."
[0121] 11. In the 3D menu, select "Height/Color view" to identify
elements or protuberances to measure.
[0122] 12. In the 3D menu, select "Profile."
[0123] 13. With the "Profile line" tab selected obtain a
cross-section of the sample identified in Step 11, select "Line"
and using the cursor draw a line across the identified portion of
the sample. The line should bisect at least two adjacent elements
or protuberances. The peaks on the right and left side of the first
element or protuberance should be relatively planar (difference in
height less than 10 percent).
[0124] 14. The height of the element or protuberance may then be
measured using the VHX-5000 Communication Software Ver 1.5.1.1 by
selecting the "Pt-Pt" vertical measurement tool to measure the
element or protuberance peak height. If the height difference
between the peaks is more than 10 percent select another first
element or protuberance to measure. Typically the element or
protuberance peak height was measured for three different peaks and
the average of the three measurements was reported.
[0125] Two dimensional, in-plane measurements of tissue products
may be made as follows:
[0126] 1. Turn the digital microscope on, and follow standard
procedures for XY stage Initialization [Auto]
[0127] 2. Turn the microscope magnification to the desired
magnification--100.times. for tissue sheet samples or 20.times. for
papermaking fabrics.
[0128] 3. Place the sample on the stage with the elements or
protuberances facing up toward the lens.
[0129] 4. If the sample does not lie flat, place weights as needed
along the perimeter to make sample lie flat against the stage
surface.
[0130] 5. Use the focus adjustment to bring the sample into sharp
focus.
[0131] 6. Select "Stitching" in the main menu. Select "2D
stitching."
[0132] 7. Set the stitching method by selecting "Stitch around the
current position."
[0133] 8. Select the Z set to set the upper and lower composition
range. The upper limit should be set by going higher than the
highest focal point that is clear. The lower limit should be set by
going lower than the lowest focal point that is clear. After
setting the upper and lower range, click OK.
[0134] 9. Select "Start stitching," to begin acquisition of the
image.
[0135] 10. Select "complete" when the desired area has been imaged,
then "Confirm stitching results."
[0136] 11. Select "Complete (show stitched image)."
[0137] 12. From the tool bar select "Measure."
[0138] 13. Select "Plane measurement," select the appropriate
measurement tool and perform the desired measurement.
[0139] Typically the dimensions of an element or protuberance, such
as the length of a CD oriented protuberance disposed on a
papermaking fabric, were determined for three elements or
protuberances and the average of the three measurements was
reported.
[0140] The element angle of a protuberance or an element was
measured using the VHX-5000 Communication Software Ver 1.5.1.1 by
obtaining a 2-D image as described above and then, using the plane
measurement tool, a reference line was drawn perpendicular to the
machine direction axis of the fabric. A second line was drawn
substantially along the element axis. The image analysis software
was then used to determine the angle between the first and second
lines. The angle of three elements or protuberances was obtained
and the average of the three measurements was recorded as the
element angle.
[0141] The surface area of a papermaking fabric covered by
protuberances may also be measured using the VHX-5000 Communication
Software Ver 1.5.1.1. An image of the fabric was acquired at a
magnification of 20.times. and from the on-screen menu "Measure"
was selected, followed by selection of "Auto" area measurement,
then the "Color" option was selected and a measurement was taken.
Once a measurement was taken the structuring elements were filled
using the "Fill" and "Eliminate Small Grains" features, followed by
selecting a Shaping step. If there are areas of the structuring
elements that needed to be filled in, or otherwise edited to create
an accurate 2-D highlight of the structuring elements, an accurate
area representation was created by selecting "Edit", "Fill." The
results were than tabulated by selecting "Next" to proceed to the
Result Display step where "Measure Result" was selected and the
calculated Area Ratio Percent was displayed. The measurement was
repeated for three distinct areas of the fabric sample and an
arithmetic average Area Ratio Percent of the measurements was
reported.
Profilometry
[0142] The valley depth and angle, as well as other fabric
properties, are measured using a non-contact profilometer as
described herein. To prevent any debris from affecting the
measurements, all images are subjected to thresholding to remove
the top and bottom 0.5 mm of the scan. To fill any holes resulting
from the thresholding step and provide a continuous surface on
which to perform measurements, non-measured points are filled. The
image is also flattened by applying a rightness filter.
[0143] Profilometry scans of the fabric contacting surface of a
fabric sample were created using an FRT MicroSpy.RTM. Profile
profilometer (FRT of America, LLC, San Jose, Calif.) and then
analyzing the image using Nanovea.RTM. Ultra software version 7.4
(Nanovea Inc., Irvine, Calif.). Samples were cut into squares
measuring 145.times.145 mm. The samples were then secured to the
x-y stage of the profilometer using an aluminum plate having a
machined center hole measuring 2.times.2 inches, with the fabric
contacting surface of the sample facing upwards, being sure that
the samples were laid flat on the stage and not distorted within
the profilometer field of view.
[0144] Once the sample was secured to the stage the profilometer
was used to generate a three-dimensional height map of the sample
surface. A 1602.times.1602 array of height values were obtained
with a 30 .mu.m spacing resulting in a 48 mm MD.times.48 mm CD
field of view having a vertical resolution 100 nm and a lateral
resolution 6 um. The resulting height map was exported to .sdf
(surface data file) format.
[0145] Individual sample .sdf files were analyzed using
Nanovea.RTM. Ultra version 7.4 by performing the following
functions:
[0146] (1) Using the "Thresholding" function of the Nanovea.RTM.
Ultra software the raw image (also referred to as the field) is
subjected to thresholding by setting the material ratio values at
0.5 to 99.5 percent such that thresholding truncates the measured
heights to between the 0.5 percentile height and the 99.5
percentile height; and
[0147] (2) Using the "Fill In Non-Measured Points" function of the
Nanovea.RTM. Ultra software the non-measured points are filled by a
smooth shape calculated from neighboring points.
[0148] (3) Using "Filtering>Wavyness+Roughness" function of the
Nanovea.RTM. Ultra software the field is spatially low pass
filtered (waviness) by applying a Robust Gaussian Filter with a
cutoff wavelength of 0.095 mm and selecting "manage end
effects";
[0149] (4) Using the "Filtering-Wavyness+Roughness" function of the
Nanovea.RTM. Ultra software the field is spatially high pass
filtered (roughness) using a Robust Gaussian Filter with a cutoff
wavelength of 0.5 mm and selecting "manage end effects";
[0150] (6) Using the "Abbott-Firestone Curve" study function of the
Nanovea.RTM. Ultra software an Abbott-Firestone Curve is generated
from which "interactive mode" is selected and a histogram of the
measured heights is generated, from the histogram an S90 value (95
percentile height (C2) minus the 5 percentile height (C1),
expressed in units of mm) is calculated.
[0151] The foregoing yields three values indicative of the fabric
topography--valley depth, valley width and wall angle. Valley width
is the Psm value having units of millimeters (mm). Valley depth is
the difference between C2 and C1 values, also referred to as S90,
having units of millimeters (mm). Valley angle is the Pdq value
having units of degrees (.degree.). Generally wall angle and valley
width are measured along a line drawn normal to the machine
direction axis of the fabric, where the line intersects at least
two adjacent MD oriented protuberances.
[0152] Before measuring element angle, care must be taken to ensure
that fabric is properly oriented before the surface map obtained by
the FRT MicroSpy profilometer, as described above. To ensure that
the warp filaments are aligned with the MD axis of the fabric and
the shute filaments aligned with the CD axis, a shute filament from
the bottom of the fabric can be pulled by hand completely across
the CD of the fabric to create a single shute filament aligned with
the fabric CD axis. The single shute filament may then be used as a
guide to align the fabric on the profilometer stage and a
profilometer scan of the fabric may be obtained as described
above.
[0153] Once a scan of the fabric is completed and the .sdf is
analyzed as described above, the element angle is determined using
the "texture direction" function under the "Studies" tab of the
Nanovea.RTM. Ultra software. Once the "texture direction" is
selected, the angle of the three most elevated features on the
fabric surface will be reported. To calculate the element angle,
the value for the protuberance of interest is selected and
subtracted from 90 degrees. The resulting value is the element
angle, having units of degrees.
Examples
Example 1--Single Ply UCTAD Bath Tissue
[0154] Tissue webs were made using a through-air dried papermaking
process commonly referred to as "uncreped through-air dried"
("UCTAD") as generally described in U.S. Pat. No. 5,607,551. Base
sheets with a target bone dry basis weight ranging of about 34
grams per square meter (gsm) were produced. The base sheets were
then converted and spirally wound into rolled tissue products as
described below.
[0155] In all cases the base sheets were produced from a furnish
comprising northern softwood kraft (NSWK) and eucalyptus kraft
(EHWK) using a layered headbox to produce a tissue web having three
layer (two outer layers and a middle layer) were formed. The two
outer layers comprised EHWK (each layer comprising 30 wt %) and the
middle layer comprised 25 wt % NSWK and 15 wt % EHWK. Strength was
controlled via the addition of starch and/or by refining the NSWK
furnish.
[0156] The tissue web was formed on a TissueForm V forming fabric,
vacuum dewatered to approximately 25 percent consistency and then
subjected to rush transfer when transferred to the transfer fabric
at a rush transfer rate of about 28 percent. The transfer fabric
was the fabric described as "Fred" in U.S. Pat. No. 7,611,607
(commercially available from Voith Fabrics, Appleton, Wis.). The
web was then transferred to a through-air drying fabric using
vacuum levels of at least about 10 inches of mercury and dried to
approximately 98 percent solids before winding. For each of the
experimental codes the through-air drying fabric comprised a woven
base fabric, a t-1205-2 woven fabric (commercially available from
Voith Fabrics, Appleton, Wis. and previously described in U.S. Pat.
No. 8,500,955) having a silicone pattern printed on the web
contacting surface. Details of the silicone pattern printed on the
each of the fabrics is provided in Table 3, below.
TABLE-US-00003 TABLE 3 Printed Nonwoven Nonwoven Pattern Percent
Code Elements Element Pattern Surface Coverage 1 Y FIG. 5A 7.5% 2,
3 Y FIG. 5B 3.75% 4 Y FIG. 2 U.S. Pat. No. 17.95% 8,940,376
[0157] The base sheet webs were converted into various bath tissue
rolls. Specifically, base sheet was calendered using a single
conventional polyurethane/steel calenders comprising a 40 P&J
polyurethane roll on the aft side of the sheet and a standard steel
roll on the fabric side: The calender load was 50 pli. The
calendered sheet was then spirally wound about a core. All rolled
products comprised a single ply of base sheet. The finished
products were conditioned and the physical properties tested. The
results of the physical testing are summarized in Table 4 and 5,
below.
TABLE-US-00004 TABLE 4 Basis Sheet Roll Weight Caliper Bulk
Firmness Bulk Roll Code (gsm) (microns) (cc/g) (mm) (cc/g)
Structure 1 32.2 505 12.73 6.3 12.73 1.02 2 28.5 431 13.30 6.3
11.46 0.78 3 28.2 439 13.30 6.0 11.79 0.86 4 33.2 475 12.36 6.1
12.34 0.96
TABLE-US-00005 TABLE 5 MD GMT Tensile Stretch GM GM Slope Stiffness
Code (g/3'') Ratio (%) TEA (g) Index 1 655 2.06 17.4 5.35 5149 7.87
2 746 2.24 12.0 6.72 5066 6.79 3 758 2.23 11.4 6.05 5126 6.76 4 662
2.07 19.0 5.85 4250 6.79
[0158] Codes 2 and 3, which represent one embodiment of the present
invention, were analyzed by microscopy as described herein. The
codes generally had a discrete CD elements have a length of about 7
mm and had an element angle of about 35 degrees. The product
comprised discrete valleys having a maximum length of about 26 mm.
Further, the CD elements had a height of about 375 .mu.m and the MD
elements had a height of about 350 .mu.m.
Example 2--Single Ply UCTAD Towel
[0159] Base sheets were prepared substantially as described in
Example 1, except that the target base sheet basis weight was 38
gsm and the two outer layers comprised EHWK (each layer comprising
30 wt %) and the middle layer comprised 40 wt % NSWK. Strength was
controlled via the addition of CMC, Kymene and/or by refining the
NSWK furnish of the center layer.
[0160] For each of the experimental codes the through-air drying
fabric comprised a woven base fabric, a t-1205-2 woven fabric
(commercially available from Voith Fabrics, Appleton, Wis. and
previously described in U.S. Pat. No. 8,500,955) having a silicone
pattern printed on the web contacting surface. Details of the
silicone pattern printed on the each of the fabrics is provided in
Table 6, below.
TABLE-US-00006 TABLE 6 Printed Nonwoven Nonwoven Pattern Percent
Code Elements Element Pattern Surface Coverage 5 Y FIG. 5A 7.5% 6 Y
FIG. 5B 3.75% 7 Y FIG. 2 U.S. Pat. No. 17.95% 8,940,376
[0161] The base sheet webs were converted into various bath tissue
rolls. Specifically, base sheet was calendered using a single
conventional polyurethane/steel calenders comprising a 40 P&J
polyurethane roll on the aft side of the sheet and a standard steel
roll on the fabric side: The calender load was 50 pli. The
calendered sheet was then spirally wound about a core. All rolled
products comprised a single ply of base sheet. The finished
products were conditioned and the physical properties tested. The
results of the physical testing are summarized in Tables 7 and 8,
below.
TABLE-US-00007 TABLE 7 Basis Sheet Roll Weight Caliper Bulk
Firmness Bulk Roll Code (gsm) (microns) (cc/g) (mm) (cc/g)
Structure 5 36.0 691 19.2 6.74 17.85 1.81 6 35.6 698 19.6 6.88
17.67 1.81 7 34.4 701 20.4 6.84 18.47 1.89
TABLE-US-00008 TABLE 8 MD GMT Tensile Stretch GM GM Slope Stiffness
Code (g/3'') Ratio (%) TEA (g) Index 5 1974 1.13 18.9 16.19 8070
4.09 6 2079 1.26 18.7 16.64 8288 3.99 7 2210 1.43 18.2 17.21 10275
4.65
[0162] Code 6, which represent one embodiment of the present
invention, was analyzed by microscopy as described herein. Images
of the inventive code are shown in FIGS. 6-9. The code generally
had discrete CD elements having a length of about 7 mm and an
element angle of about 35 degrees. The product comprised discrete
valleys having a maximum length of about 26 mm. Further, the CD
elements had a height of about 800 .mu.m and the MD elements had a
height of about 650 .mu.m.
Example 3--Multi-Ply UCTAD Towel
[0163] Base sheets were prepared substantially as described in
Example 1, except that the target base sheet basis weight was about
27 grams per square meter (gsm). In all cases the base sheets were
produced from a furnish comprising northern softwood kraft (NSWK)
and eucalyptus hardwood kraft (EHWK) using a layered headbox to
produce a tissue web having three layers (two outer layers and a
middle layer) were formed. The two outer layers comprised EHWK
(each layer comprising 20 wt % of the tissue web) and the middle
layer comprised NSWK (middle layer comprised 60 wt % of the tissue
web). Strength was controlled via the addition of
carboxymethylcellulose (CMC) and a permanent wet strength resin,
and/or by refining the NSWK furnish.
[0164] For each of the experimental codes the through-air drying
fabric comprised a woven base fabric, a t-1205-2 woven fabric
(commercially available from Voith Fabrics, Appleton, Wis. and
previously described in U.S. Pat. No. 8,500,955) having a silicone
pattern printed on the web contacting surface. Details of the
silicone pattern printed on the each of the fabrics is provided in
Table 9, below.
TABLE-US-00009 TABLE 9 Printed Nonwoven Nonwoven Pattern Percent
Code Elements Element Pattern Surface Coverage 8 Y FIG. 5A 7.5% 9 Y
FIG. 5B 3.75% 10 Y FIG. 2 U.S. Pat. No. 17.95% 8,940,376
[0165] The base sheet, prepared as described above, was converted
into a two-ply rolled towel product. Specifically, the base sheet
was calendered using a patterned steel roll and a 40 P&J
polyurethane roll at a load of 30 pli. The calendered base sheet
was then converted to a two-ply product by embossing and laminating
substantially as described in co-pending International Application
No. PCT/US18/58322 and illustrated in FIG. 1A thereof. The engraved
roll had a chevron-like pattern that provided the product with an
embossed area of about 7 percent. The two-ply tissue product was
then converted into a rolled towel product and subjected to
physical testing, the results of which are shown in Tables 10 and
11, below.
TABLE-US-00010 TABLE 10 Basis Sheet Roll Weight Caliper Bulk
Firmness Bulk Roll Code (gsm) (microns) (cc/g) (mm) (cc/g)
Structure 8 52.0 963 18.5 7.0 18.45 2.53 9 54.0 1072 19.9 6.6 17.77
2.89 10 53.3 988 18.5 6.8 18.01 2.60
TABLE-US-00011 TABLE 11 MD GMT Tensile Stretch GM GM Slope
Stiffness Code (g/3'') Ratio (%) TEA (g) Index 8 3208 1.26 16.4
26.01 12349 3.85 9 1974 1.13 16.4 16.64 8288 3.99 10 3131 1.19 15.5
22.32 12636 4.04
Embodiments
[0166] In a first embodiment the present invention provides a
spirally wound single tissue sheet having a fabric side and an
opposite air contacting side and a machine direction and a
cross-machine direction, the ply having a basis weight from 30 to
60 gsm and a geometric mean tensile (GMT) strength greater than
about 1,500 g/3'', wherein the air contacting side of the ply
comprises a plurality of discrete valleys having a length greater
than about 10 mm.
[0167] In a second embodiment the present invention provides the
product of the first embodiment further comprising a plurality of
substantially continuous MD oriented elements spaced apart from one
another in the CD.
[0168] In a third embodiment the present invention provides the
product of the first or the second embodiments further comprising a
plurality of discrete CD oriented elements spaced apart from one
another in the MD.
[0169] In a fourth embodiment the present invention provides the
product of any of the first through third embodiments wherein the
plurality of discrete valleys have first and second sidewalls
formed from a first and a second MD oriented element and first and
second endwalls formed from a first and a second CD oriented
element.
[0170] In a fifth embodiment the present invention provides the
product of any of the first through fourth embodiments wherein the
plurality of MD oriented elements are substantially parallel to one
another and have an element angle from about 0.5 to about 10
degrees.
[0171] In a sixth embodiment the present invention provides the
product of any of the first through fifth embodiments wherein the
plurality of CD oriented elements are substantially parallel to one
another and have an element angle from about 20 to about 40
degrees.
[0172] In a seventh embodiment the present invention provides the
product of any of the first through sixth embodiments wherein the
plurality of CD oriented elements have a length from about 3.0 to
about 10.0 mm.
[0173] In an eighth embodiment the present invention provides the
product of any of the first through seventh embodiments wherein the
plurality of CD oriented have a height from about 700 to about 900
.mu.m.
[0174] In an ninth embodiment the present invention provides the
product of any of the first through eighth embodiments wherein the
discrete valleys have a length from about 10 to about 30 mm and a
width from about 1.0 to about 3.0 mm.
[0175] In a tenth embodiment the present invention provides the
product of any of the first through ninth embodiments having a
caliper greater than about 700 .mu.m and a roll structure greater
than about 1.75, or a roll bulk greater than about 16 cc/g and a
roll structure greater than about 1.75, or a firmness from about
6.0 to about 8.0 and a roll structure greater than about 1.75.
* * * * *